HELP PLS!! WILL GIVE BRAINLIEST What is a catalyst? A a substance that slows a reaction down without being used up itself in a reaction. B a substance that is used up while speeding up a reaction. C a reactant that is added to speed up a reaction. D a substance that increases the rate of a reaction without being used up itself in a reaction.

When the earth was formed and cooled, why did nickel and iron end up in the center of the earth while basalt and granite ended up in the outer layers

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

An experimental procedure requires a 10 ml of acid to be dissolved